A hybrid vehicle uses a driving power of an engine and a motor, either in combination or alone. Such a hybrid vehicle can travel using only the driving power of the motor at normal times or driving power of the engine together with the motor. When the power of an internal high-voltage battery is insufficient, or when sufficient driving power cannot be obtained only by the motor, the engine supplies the driving power.
When the driving power of the engine is not required at normal times, connection between the engine and the motor or between the engine and a gearbox is released, so that a loss of power caused by the engine, which is not driven, must be reduced. For this, a clutch operated using oil pressure is provided between the engine and the motor or between the engine and the gearbox, and controls a transmission of driving power of the engine.
The clutch is operated by a hydraulic cylinder separately installed to connect or disconnect the clutch, and the connection of the clutch is made according to the operation of the hydraulic cylinder. The oil pressure applied to the hydraulic cylinder must be suitably controlled according to a preset control level. For this, a separate oil pressure sensor is provided on the hydraulic cylinder connected to an oil pump or on an oil pressure line in which oil is applied to the hydraulic cylinder, and is configured to detect the oil pressure applied to the hydraulic cylinder and apply a pressure suitable for a current condition via a feedback operation.
Further, in an oil pressure sensor, an offset generally occurs for an initial value thereof depending on a production process and design of the oil pressure sensor. For example, in the case where the oil pressure sensor is designed to output the initial value thereof as 0 V, if the oil is not pressurized in an oil pressure line, the initial value must be 0 V, but, due to the above-described factors, an offset such as 0.1 V or 0.3 V occurs in the initial value.
Therefore, there is a need to correct the offset and obtain the output value of the oil pressure actually generated. Conventional technology is configured such that a correction starts at the same time that the oil pump is driven, upon correcting the offset.
However, when the oil pump is driven, oil pressure caused by an oil leakage in the oil pressure line, which occurs in a solenoid valve or the like, is recognized as the offset by the oil pressure sensor. Therefore, the correction caused by the pressure of leaked oil is also performed together with the correction of the offset, thus causing a problem in that oil pressure higher than a suitable value is actually applied to the oil pressure line or the hydraulic cylinder.
The foregoing is intended merely to aid in the better understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.